UTF8 Byte Order Mark (BOM) is sequence of bytes for represent the file as UTF8. The sequence is hexadecimal EF BB BF value also you can see it at the beginning of the file as . When these symbols is used the text editor recognizes that file as UTF8.
In most cases it creates a problem for PHP programmers. When php file is interpreted these symbols sent to the output directly (because there are not inside of <?php ?> tags). If the php file modifies or sends headers, BOM is sent before the headers(as an output) and sending headers fails. Usually you see such error:
Warning: Cannot modify header information – headers already sent by (output started at /path/to/php/public_html/config.php:28) in /path/to/php/public_html/index.php on line 101
The solution is to remove the UTF8 BOM signature from the PHP files. On Notepad++ or EmEditor you can save the file without UTF8 BOM. Another method is to open the files with the editor with can’t read utf8 and remove these byte order manually.
The easiest way is bomremover tool. You can get it from http://code.google.com/p/bomremover/ .
#cd /path/to/php/files/ #/path/to/bomremover/bomremover.sh -r
This will recursively locate the files and remove the BOM from files.
For removing BOM from a single file:
#cd /path/to/php/files/ #/path/to/bomremover/bomremover.sh index.php
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